Tuesday, July 26, 2011

Lunar Mining [Part Three]: Lunar Considerations

This is our third post about whether or not it makes sense, economic especially, to mine the Moon for resources. We already tackled the He-3/Helium-3 meme in an earlier post. Now we are considering whether or not it makes sense to extract Platinum Group Metals or Rare Earth Elements from the Moon for terrestrial use. Ie does it make sense to go mine the Moon? Should Team Phoenicia be outfitting our rover, Victory on Pangaea, as part of an effort to boot strap this nascent industry?

This post will deal with working on the Moon and the specific issues that must be taken into consideration. This is as much meant to be a contrast with what is done here on Earth and a consideration of what must be adapted and changed to make it work for the Moon. Where there are problems with working on the Moon or regulatory issues, this will also be covered.

However, the main economics thrust (and conclusion) will await another post, probably next week or the week after since the GLXP Team Summit will be preoccupying the Team: since we're largely local, we are sooooooo going to smack down the XPF and PTS on the burger munching.

The Obvious Differences:

The lunar environment is like nowhere on earth, not even in the most extreme locales where mining takes place, or even could take place just as a demonstration come close to matching the extremes of even the most benign locations of the Moon. These differences are worth touching on if we are go examine what would be needed to produce lunar mines. The some of the environmental factors that are radically different than on Earth include the fact the Moon lacks an atmosphere, radically different day/night cycle, and the ever present regolith. We will be lightly discussing each of these.

Working in a vacuum

Working in an atmosphere is something that we all take for granted. It has been said that nature abhors a vacuum. In reality, it seems that nature actually abhors an atmosphere. If the Moon had anything close to an atmosphere, it has been lost in the eons long since past. Technically, the Moon does have an atmosphere, but its something that's so tenuous that for all intents and purposes any operations on the Moon must be treated as working in the hardest of vacuums. At least until we finally terraform the Moon...

Since we are only now reaching out to the Moon once more to traverse its surface, its just mildly premature to discuss shirtsleeve mining techniques, nevermind terraforming Luna herself. Besides the lack of breathable atmosphere on the Moon meaning that any human miners would need to be spacesuits and an extraordinary logistics train for supplies, there are other considerations that even anaerobic robots would need to take into account. Since we are participating in a prize to land uninhabited rovers on the Moon, we'll focus on robotic concerns.

The foremost of those considerations is heat. Computers these days generate a fantastic amount of heat. In fact supercomputing centers spend as much money on the power to cool the computers that everyone assume aspire to Skynet-hood as it does to just run them. Even your PC probably uses over 800 watts of power...and that is converted into heat. Heat that must go somewhere. In an atmosphere, that's an easy thing to take care of. It gets cooled by running air over it. Convention is the fastest way to cool something as its heat is imparted into the vast heat sink that is the air we breath. However, lacking this, the Moon forces something operating on it to radiate away the heat. This is orders of magnitude slower and as the some of the experts in the field have put it, even 50 watts of power can be your bane over time in a vacuum.

Any lunar excavator would need to have a carefully and extensively planned system of radiator fins or a massive heat sink that it would need to offload the heat from after a period of time to another system that might have that labyrinthine peacock tail of radiator fins. Either you are trading physical complexity and limitations on mining behavior in order to protect the cooling apparatus or you are adding significant complexity to the control side of the mining robot. Dumping heat in a vacuum has been dealt with and is a known problem. However, it has not been dealt with while also designing a mining vehicle. To do so will be most definitely nontrivial.

The Lunar Light Cycle

The Moon does not have the terrestrial night cycle. On Earth, we have a 24 hour light cycle where we shift from day to night and back again. This relatively short cycle combined with the atmosphere keep the Earth's surface within certain temperature ranges. As brutal as many of the terrestrial environments are, the day-night cycle on the Moon alone easily outruns the competing equivalents on Earth.

Lunar nights last 354 hours. This is more than 14 days long. Any system of solar power will need to have energy storage or a backup that will last two weeks. To do this would require a solution that is either massive (or heavy in common terms, like extensive batteries) and/or a political hot potato (nuclear power).

The heating and cooling cycle from the lunar light cycle is very difficult to deal with, too. The surface temperatures at the equator swing 300 C from its lows around -180 C to 123 C. Any materials that the equipment is made form must be able to handle those temperature swings. That thermal loading from the sun is significantly higher than on Earth. Getting rid of that heat is something that must be taken into consideration for all mining operations.

In the permanently shaded regions, while, the temperature does not fluctuate, it is an estimated -233 C.

Regolith

Lunar regolith is truly nasty stuff. It is one of the most abrasive substances known to man. In any operation equipment that is developed is going to need to deal with this fact. Machines wear out from grit getting into them here on earth. When it is far more hostile than any sand on earth, the results could be catastrophic. There are lunar regolith simulants that can be tested against, but the basic design consideration is still present.

Location, Location, Location:

The final consideration is a doozie: the moon is far away. On the cosmic scale, the Moon is sitting in our laps. On the scale of working on active mines, it could not be further away. In all probability, there will be no one there to fix things for several years. Troubleshooting remotely is quite the challenge: just as the MER team and what happened with Spirit. And! What may be acceptable for an explorer would almost certainly not be for a production mine: days, even weeks of being stuck could be disastrous financially.

A lunar mine truck stuck on the ramp could permanently shutdown the mine. Planned for such events - the stuff that we take for granted on our own rock, like being able to kick the tires or manually and easily hook up a winch or whatnot - is not so easy roboticly, nevermind on the Moon.

Furthermore, just getting to and from the Moon is nontrivial. The more equipment you take up, the more expensive it is. The more material you bring down, the more expensive it is. If you askew more for more complex equipment, it increases the likelihood of breakdown and of greater cost. Cost, money, profits, and some analysis however, are the next post's subjects as we use it to wrap up our lunar mining posts.